Suppression of avidin processing and presentation by mouse macrophages after sublethal exposure to dieldrin

Alterations in macrophage phagocytosis and inflammatory tone following exposure to the organochlorine compounds oxychlordane and trans-nonachlor

The role of macrophages in the innate immune response cannot be underscored however recent studies have demonstrated that both resident and recruited macrophages have critical roles in the pathogenesis of metabolic dysfunction. Given the recent data implicating exposure to persistent organic pollutants (POPs) in the pathogenesis of metabolic diseases, the current study was designed to examine the effects of the highly implicated organochlorine (OC) compounds oxychlordane and trans-nonachlor on overall macrophage function. Murine J774A.1 macrophages were exposed to trans-nonachlor or oxychlordane (0 - 20 µM) for 24 hours then phagocytosis, reactive oxygen species (ROS) generation, mitochondrial membrane potential, caspase activities, pro-inflammatory cytokine production, and macrophage plasticity were assessed. Overall, exposure to oxychlordane significantly decreased macrophage phagocytosis while both OC compounds significantly increased ROS generation. Exposure to trans-nonachlor significantly increased secretion of tumor necrosis factor alpha (TNFα) and interleukin-6 whereas oxychlordane had a biphasic effect on TNFα secretion. However, both oxychlordane and trans-nonachlor decreased basal expression of the M1 pro-inflammatory marker cyclooxygenase 2. Taken together, these data indicate that exposure to these two OC compounds have both compound and concentration dependent effects on macrophage function which may alter both the innate immune response and impact metabolic function of key organs involved in metabolic diseases.

The cell cultures and the use of haemocytes from marine molluscs for ecotoxicology assessment

Among aquatic organisms suitable for biological monitoring, molluscs occupy a prominent place due to their wide geographic distribution, their abundance and accessibility in the field as well as in aquaculture. Molluscs reflect the degree of environmental contamination and are the most useful bioindicator tools. The study of modulation of immune system or immunomodulation in marine molluscs has become one of the privileged ways for evaluating the physiological effects of environmental factors. Physiological responses of molluscs to environmental stresses could be mediated by haemocytes. These cells are continually exposed to the external environment due to the open circulatory system of molluscs and are affected by pollutants. In fact, several studies showed the effects of different environmental contaminants on haemocyte functions (viability, phagocytosis, ROS production) as well as on proteins involved in cytoskeletal structure maintenance using the in vitro approaches. In ecotoxicology, in vitro approach is an alternative to animal testing due to the reduced use of experimental animals, low cost and rapid performance. Although several studies showed the importance of using in vitro cell models to determine the effects of different environmental contaminants on haemocyte parameters in marine molluscs, a few reviews highlight these effects. The main purpose of this paper is to summarize the recent data on the effect of some xenobiotics on haemocyte parameters in some mollusc species and then suggest future research prospects.

Immunomodulatory effect of various anti-parasitics: a review

This paper reviews the immunomodulatory effects (immunosuppression or immunoactivation) of various anthelmintics including levamisole, fenvalerate, dieldrin, carbofuran, aminocarb, thiabendazole, fenbendazole, oxfendazole and ivermectin. The induced modulation of immune function may occur via direct and/or indirect mechanisms. The immunomodulatory effects of these anti-parasitics have been studied in a variety of bacterial (e.g. brucellosis, salmonellosis, paratuberculosis, mastitis), viral (e.g. infectious bovine rhinotracheitis, Herpes, foot and mouth disease), parasitic (e.g. onchocerciasis, coccidiosis, ascariasis, schistosomiasis) and neoplastic diseases. Some antiparasitics have also been used to boost immunity in a number of human diseases including leprosy, Hodgkin's disease, rheumatoid arthritis, and in adjuvanted therapy of colorectal cancer. The ability to stimulate the immune response of animals offers a new means of disease intervention. Future research on immunomodulatory effects of anti-parasitics, for humans and domestic farm animals, will provide additional methods of treating immunosuppressed subjects. The immunopotentiating or immunosuppressing activity of anti-parasitics will dictate whether co-administration of vaccines and anthelmintics or administration of vaccines during the window of immunoactivation is justified or not.

Effects of exposure of Mya arenaria and Mactromeris polynyma to contaminated marine sediments on phagocytic activity of hemocytes

Two species of bivalves, Mya arenaria and Mactromeris polynima, were exposed to contaminated marine sediments from Baie des Anglais, Quebec, for a period of 10 and 12 weeks, respectively, in order to determine if there was an effect on the phagocytic activity of hemocytes from each species. These sediments contain elevated levels of both PAHs and PCBs. Uncontaminated beach sand was used as control sediments. After a period of 4 weeks, each species of bivalves were sampled and hemocyte phagocytic activity was monitored by flow cytometry. While phagocytosis by hemocytes from M. polytiyma was significantly suppressed, those from M. arenaria were not different from beach sand-exposed controls. At the end of the exposure period, the phagocytic activity of hemocytes from both species was suppressed. Physiological parameters such as mantle proteins or malondialdehyde levels, total protein and total glycogen levels in the digestive gland were not affected by exposure to contaminated sediments. Moreover, the suppression of phagocytosis was well correlated with the transfer of contaminants from the sediments to the bivalves and their subsequent bioaccumulation, as demonstrated by the PCB body burden. These results support the use of bivalves as good sentinel species to survey sediment contamination and the usefulness of hemocyte phagocytic activity as a sensitive biomarker of exposure to organic contaminants.

Phagocytic activity of marine and freshwater bivalves: in vitro exposure of hemocytes to metals (Ag, Cd, Hg and Zn)

We measured non-specific immune function of various bivalves from marine (Cyrtodaria siliqua, Mactromeris polynyma, Mesosdesma arctatum, Mya arenaria, Mya truncata, Mytilus edulis, Serripes groenlandicus, Siliqua costata) and freshwater environments (Dreissena polymorpha and Elliptio complanata). We used flow cytometry to quantify the phagocytosis of fluorescent microspheres by hemocytes exposed in vitro to increasing levels of various metal compounds (AgNO(3), CdCl(2), CH(3)HgCl, HgCl(2) and ZnCl(2)). In some species, low doses of mercury (organic and inorganic) and Zn suggest a hormesis-like stimulation of phagocytic activity. At higher levels of exposure, all metals tested induced a significant dose-related inhibition of hemocyte phagocytosis. The species-specific sensitivity of the assay was determined by comparing the in vitro exposure using the metal concentration inducing a 50% suppression (EC(50)) of the phagocytic activity. Different species expressed different levels of sensitivity. Our results show the variability of the toxic response of different species within a group of similar organisms. It also highlights the need to consider species-species differences in ecotoxicological risk assessment.

Flow cytometry as a tool to monitor the disturbance of phagocytosis in the clam Mya arenaria hemocytes following in vitro exposure to heavy metals

The effectiveness of toxicology biomonitoring programs could be improved by the addition of sensitive biomarkers. In this study the cell viability and sensitivity of phagocytic function of phagocytes from bivalves (Mya arenaria) to selected heavy metals were measured by flow cytometry, a novel approach. Hemocytes (phagocytes) collected from bivalves by puncture of the posterior adductor muscle were incubated in vitro for 18 h in hemolymph containing 10(-9)-10(-3)M of cadmium chloride, zinc chloride, mercuric chloride, methylmercury chloride or silver nitrate, before determining their capacity to phagocytose fluorescent latex beads by flow cytometry. Heterogeneity of the hemocyte cell population was determined by forward scatter (FSC) and side scatter (SSC) cytometric profile which showed two distinct cell populations. At low doses (10(-9), 10(-8) M), all the metal compounds studied stimulated phagocytic activity except silver nitrate. At higher levels of exposure (10(-6), 10(7) M), all metals caused a significant concentration-related decrease in hemocyte phagocytosis activity. From the concentration of each metal inducing 50% suppression (IC50) of the phagocytic activity, the immunotoxic potential of metals with respect to phagocytic function can be ranked in the following increasing order: ZnCl2 < CdCl2 < AgNO3 < HgCl2 < CH3HgCl. Parallel analysis of hemocyte viability showed that suppression of phagocytosis by heavy metals was not solely related to a decreased cell viability. These results reveal the high but different degree of sensitivity of the phagocytosis activity of bivalves with respect to heavy metals, as measured by flow cytometry, and demonstrate that flow cytometry is a potentially useful tool in ecotoxicological monitoring.

Genotoxicity testing of six insecticides in two crosses of the Drosophila wing spot test

Among the great variety of genotoxicity assays available, the wing spot test in Drosophila melanogaster has some characteristics that make it very suited for the screening of genotoxic activity, i.e., it is an easy and inexpensive assay using a eukaryotic organism in vivo. One of the most interesting characteristics of the assay is its capacity to detect genotoxic activity of promutagens without the necessity of an exogenous metabolic activation system. In this paper we present results obtained with a recently developed high bioactivation cross of the wing spot test (NORR cross). The positive results obtained with the five well-known procarcinogens 7, 12-dimethylbenz[a]anthracene, N-nitrosopyrrolidine, p-dimethylaminoazobenzene, diethylnitrosamine and urethane clearly show that the NORR strains are similar to the other high bioactivation strains previously described, but they lack their methodological disadvantages. We have tested six insecticides, which are characterised by having contradictory results in other genotoxicity tests, using both the standard and the high bioactivation (NORR) cross. The six insecticides analysed are the pyrethroid allethrin, the methylenedioxyphenolic compound piperonyl butoxide, the chlorinated hydrocarbons dieldrin and endrin, and the organophosphates dimethoate and malathion. We obtained negative results for all six compounds. Our results show the suitability of the wing spot test for the evaluation of compounds at the first level of genotoxicity testing.

Immunotoxicity of pesticides: a review

The intricate balance that is the hallmark of the immune system shows vulnerability to any chemical, including pesticides, that can cause structural and functional alterations to the system. The immunotoxic effects of xenobiotics include: histopathologic effects in immune tissues and organs; cellular pathology; altered maturation of immunocompetent cells; changes in B and T cell subpopulations; and functional alterations of immunocompetent cells. Pesticides, including fungicides, herbicides, and insecticides, are the only class of chemicals deliberately released into the environment because of their toxicity. Around the world, millions of people are exposed to pesticides at work and/or in their home. This article reviews evidence, from animal and human studies, on the effects of pesticides on the immune system.

In vivo indomethacin reverse exercise-induced immunosuppression in rats

The effect of oral indomethacin on the immunosuppressive effect of exercise was examined in exercised untrained female Wistar rats immunized with sheep red blood cell (SRBC) antigens. Intensity of the 1 h exercise was controlled by 0-50 kPa air pressure, generated by a compressor located at the bottom of a water tank, during continuous swimming of the rats, previously immunized with SRBC. After 48-72 h, depending on the ip (intraperitoneal) or iv (intravenous) route of SRBC immunization, the exercise suppressed humoral PFC response and augmented phagocytosis of peritoneum macrophages. These effects occurred only when exercise was performed at 48 h after antigen injection. Animals receiving indomethacin, however, did not show any exercise-related suppression of the PFC response. The data suggest a relationship between exercise-induced immunosuppression and possible increased in vivo prostaglandin synthesis during the intense exercise. Overall, exercise-related suppression of humoral PFC response was dependent on the intensity of the exercise, was time specific, and was reversible by pharmacological blockade of the cyclooxygenase pathway of prostaglandin synthesis.

Cytometric profile of molybdenum-induced contact sensitization versus a strong allergen reaction to oxazolone in murine auricular lymph node (ALN) test

Induction of contact hypersensitivity (CH) by molybdenum chloride (MoCl5) was determined by auricular lymph node (ALN) test in C57B1/6 mice. The ALN test was further improved by immunophenotyping and cytometric analysis of subset-specific cell in the draining node. Skin sensitization was induced by topical ear exposure to 1.0-50% oxazolone and resulted in a strong dose-related ALN reaction. Analogous exposure to MoCl5 resulted in a weaker but marked dose-related reaction, also manifested as an increase in cell number/ALN. Other differences between the oxazolone-induced strong sensitization and the MoCl5-related ALN reaction were: (1) an increase in the total number of Ig+ cells, which was, however, unchanged in the MoCl5-exposed mice; (2) a significant increase in the total number of large/activated T-cell subsets; and (3) a marked shift in the relative percentage of gated large/activated subsets of ALN cells, which was not observed in the MoCl5-exposed animals. Thus, it appeared that the molybdenum exposure induced a nonspecific increase in the cell number/ALN and was not accompanied by any marked activation of the T-cell subsets. Immunotoxicity of a 14 day subchronic exposure to MoCl5 at 1-100 ppm in food was studied by quantification of splenic humoral IgM response to sheep erythrocytes (SRBC). Plaque-forming cells (PFC) and enzyme-linked immunosorbent assay (ELISA) revealed unchanged humoral exposure in MoCl5-exposed mice. Cytometric assay of fluorescent beads uptake showed unchanged phagocytic activity of peritoneal macrophages from the MoCl5-exposed mice. Immunophenotyping of CD4+, CD8+, Thy 1.2+ and Ig+ cells revealed no effect of MoCl5 exposure on the total count of cell subsets in the ungated populations of spleen, lymph nodes and peripheral blood cells. Molybdenum chloride should thus be considered as a non-immunotoxic and a weak, nonspecific contact irritant.

Modulation of exercise-induced immunosuppression by dietary polyunsaturated fatty acids in mice

The possible interaction between intense exercise, known to suppress the immune response, and nutritive factors, such as polyunsaturated fatty acids (PUFA), was examined in inbred female C57Bl/6 mice. The animals received for 8 wk either a natural ingredient diet or a diet supplemented with 10 g/100 g linseed oil containing over 50% of 18:3 (n-3) alpha-linoleic acid. Other groups received PUFA containing only traces of 18:3 (n-3) fatty acid; beef tallow, containing mostly 18:1 (n-9) saturated fat, safflower oil, an 18:2 (n-6) PUFA, and fish oil, containing longer chain (n-3) PUFA. Each dietary group was divided into two subgroups: sedentary diet controls and exercised animals. Exercise consisted of continuous swimming at high intensity until exhaustion. It was shown in three separate experiments that (1) the primary humoral response to sheep red blood cells, determined by the plaque-forming cell (PFC) assay, was affected by PUFA diet in sedentary animals in the order beef tallow > control diet > safflower oil > fish oil > linseed oil, and (2) the PFC response was suppressed by the exhaustive exercise, as compared to sedentary controls, except for animals fed 18:3 (n-3) linseed oil, where the normal response was noted. Phagocytosis of fluorescent microspheres by peritoneal macrophages, determined by flow cytometry, was significantly lower in exercised animals receiving the linseed oil diet, whereas other diets either increased or did not significantly change the macrophage phagocytic activity, compared to the sedentary diet controls. Spleen lymphocyte subsets were unchanged in exercised animals except for a marked shift from the lymphoid peak toward the erythroid peak. Generally, our data showed a marked immunomodulatory effect of 18-3 (n-3) alpha-linoleic acid on the exhaustive exercise-related immunosuppression, as compared to the effects of other selected PUFA.

Cytometric profiles of bone marrow and spleen lymphoid cells after mercury exposure in mice

The potential immunotoxic effects of mercury chloride on murine bone marrow (bm) cell subpopulations, including analysis of maturation patterns for B-cells, were evaluated by flow cytometric analysis. CD-1 outbred mice were exposed for 28 days to relatively low doses of 25-100 ppm HgCl2 in drinking water and the mercury-related functional cellular changes were validated in a macrophage phagocytosis assay. Lymphocyte subsets from the bone marrow population were stained with PNA lectin and a panel of monoclonal antibodies against cell surface antigens. The incidence of subset-specific staining was also monitored in spleens and thymuses. A dose-effect correlation was noted for the mercury-related activation of macrophage phagocytosis. Subchronic exposure to mercuric chloride resulted in a transient (7-14 day) decrease of the lymphoid/total bm cell ratio and affected the incidence of splenic T-cell subsets, however, without a clear dose-response correlation. The B-cell population in spleen and maturation patterns of B-cells in bm appeared to be unaffected by the mercury exposure. Overall, cytometric analysis of lymphoid cell subsets in murine bone marrow revealed transient and subset-non-specific cell fluctuations after subchronic exposure to inorganic mercury.

Immunotoxicity of subchronic versus chronic exposure to aldicarb in mice

In this study we compared the immunotoxicity of subchronic vs chronic exposure to the aldicarb insecticide at a relatively low, 0.1-10 ppb, level in drinking water. The immunotoxicity of aldicarb was evaluated in 28- and 90-day studies by determination of the humoral, cellular and nonspecific immunity in inbred C57BL/6 mice. Quantification of splenic plaque-forming cells (PFC) to sheep erythrocytes (SRBC), mitogen activation of spleen lymphocytes, mixed lymphocyte reaction (MLR) and the cytofluorometric assay of the phagocytic uptake of fluorescent beads were among the parameters studied. Neither the cell viability nor the splenic cell count was affected by the insecticide exposure. Immunophenotyping and cytometric determination of L3T4+, Lyt2+ and Ig+ cells revealed no effect of the insecticide exposure on the total count of cell subsets in the ungated splenocyte population. However, a marked shift in the percentages of L3T4+ and Lyt2+ cells was noted after subchronic exposure to 1 and 10 ppb aldicarb, possibly indicating activation of these splenic T-cell subsets. Subchronic aldicarb exposure significantly suppressed the splenic PFC response to SRBC at 1 ppb dose, however, no dose-effect correlation could be concluded. Similarly, no dose-effect correlation was observed for subchronic aldicarb-related changes in mitogen responses. Subchronic exposure to aldicarb had no statistically significant effect on the mixed lymphocyte reaction (MLR) or on the macrophage phagocytosis. Chronic exposure to 0.1-10 ppb aldicarb did not affect any of the parameters measured, including the cell subsets. Thus, aldicarb-related changes in immune parameters, noted after a 28-day exposure, were compensated over chronic exposure to the insecticide.

Combined effects of selected insecticides on humoral immune response in mice

Biological effects data with single insecticides are far more abundant than with mixtures. These data cannot be used directly to predict the effects of insecticide mixtures. Three insecticides of different chemical classes: organochlorine; dieldrin, organophosphate; malathion, and carbamate; carbofuran, previously evaluated for their immunotoxic potential, were selected for studies of combined acute exposure in C57B1/6 inbred mice. The humoral response to sheep red blood cells (SRBC) and the functional activities of peritoneal macrophages, such as phagocytosis of fluorescent beads and presentation of a single protein antigen, avidin, were examined after in vivo exposure of mice to different combinations of the selected pesticides and compared with the vehicle controls. Regarding exposure to single substances, the data confirmed the immunosuppressive potential of dieldrin and carbofuran and the immunopotentiating effect of malathion. Following the acute concomitant exposure to dieldrin/carbofuran mixture, however, values for the parameters of antigen presentation, primary IgM antibody response to SRBC antigen, and macrophage phagocytosis, returned to control or above-control values, indicating a lack of any synergistic or additive effects of the chemicals on the immune response. Thus, it was concluded the dieldrin/carbofuran mixture had an antagonistic effect on the humoral response to SRBC and the macrophage phagocytic activity, in comparison with the action of administration of each of the insecticides alone.

Limited immunotoxic potential of technical formulation of the herbicide atrazine (AAtrex) in mice

Immunotoxicity of the technical atrazine formulation, AAtrex, was examined in C57Bl/6 female mice following a sublethal exposure to equivalent 1/2-1.64 LD50 doses of the herbicide. Animal weight was not affected by the herbicide exposure. No dose-related changes could be concluded for fluctuations in organ weight, changes in the spleen cell number and cell viability. Furthermore, cytofluorometric studies showed no significant changes in the frequency of L3T4-positive and Lyt-2-positive T-cells. Functional in vitro assays of mitogen activation showed no marked effects of AAtrex exposure on lymphocyte stimulation by lipopolysaccharide (LPS), phytohemagglutinin (PHA) and concanavalin A (Con-A). In addition, sublethal exposure to AAtrex did not affect interleukin-2 (IL-2) production by splenic cells. Furthermore, no dose-related effect could be concluded from a transient suppression of a primary humoral IgM response to sheep erythrocytes (SRBC) as well as from a transient inhibition of a specific T-cell response to alloantigens in mixed lymphocyte reaction (MLR). Exposure to equiv. 1/2-1/16 LD50 doses augmented phagocytic activity of peritoneal macrophages, without any visible AAtrex dose-related effect. Normal humoral and cellular responses were restored at 14-40 days after the herbicide exposure. Overall, transient and reversible immunosuppression of humoral-mediated and cell-mediated responses and activated macrophage phagocytic activity could not be attributed to the direct chemical-related effect of sublethal exposure to AAtrex.